This invention relates to a turbine blade with impingement cooling of the thermally highly loaded outer wall sections, where at least one partition is provided in the interior of the hollow turbine blade to form a cooling-air chamber supplied with cooling air and where, with the formation of an impingement air cooling chamber, the partition is provided with a plurality of impingement air channels to apply cooling air to the remotely adjacent inner surface of the hot outer wall sections.
The efficiency of gas turbines can be improved by increasing the combustion chamber temperatures. Such temperature increase is, however, limited by the thermal loadability of the components exposed to the hot gases, in particular the stator vanes and rotor blades in the turbine stage downstream of the combustion chamber, which additionally are subject to high mechanical stresses. In order to prevent transgression of the material-specific temperature limits, the respective components and, in particular, their thermally highly loaded areas are, as is generally known, cooled with cooling air tapped from the compressor.
In the case of an impingement cooling for a turbine blade known from Specification EP 1 001 135 A2, for example, longitudinal partitions are arranged in the inner of a hollow blade confined by two side walls which, together with a side wall section, form a long cooling air supply and distribution chamber (cooling air chamber) and, adjacent to the cooling air chamber, several impingement air cooling chambers. Via the impingement air channels, the cooling air introduced into the cooling air chamber flows—consecutively or in other cases also simultaneously—into the adjacent impingement air cooling chambers, thereby intensely cooling the inner surfaces of the thermally highly loaded areas of the outer walls of the turbine blade from the inside and enabling the gas turbine to be operated with high efficiency at maximum combustion temperatures and without material damage. The impingement air channels are straight-lined, but inclined within the partition to ensure a favorable angle of impingement of the impingement cooling air onto the inner surfaces of the outer walls. In addition, the air exiting from the impingement air cooling chambers via air channels in the sidewalls of the turbine blade creates a barrier layer between the blade material and the hot gas which further reduces the thermal load of the turbine blade.
While the impingement air channels reduce the load-carrying area of the partitions supporting the outer walls, load peaks occur in the area of the impingement air channels which entail high local mechanical stresses and, in consequence, a reduction of the life of the turbine blade. Furthermore, appropriately large dimensioning of the thickness of the partitions, which would decrease the local load peaks, is to be ruled out for reasons of weight and associated loads.